Pilot flame burner, particularly for gases of low flammability



April 1967 H. EGGENSTEIN 3,315,724

PILOT FLAME BURNER, PARTICULARLY FOR GASES OF LOW FLAMMABILITY Filed July 12, 1965 United States Patent Oflice 3,315,724 Patented Apr. 25, 1967 3 315,724 PILOT FLAME BURI IER, PARTICULARLY FOR GASES F LOW FLAMMABILITY Horst Eggenstein, Erlrrath, Germany, assignor to Stadt My invention relates to a pilot flame burner for providing a keep-alive flame to ignite a main burner in a furnace, heater or other gas-fired equipment. In a more particular aspect, the invention concerns a pilot flame burner particularly suitable for operating with gases of low ignition speed, i.e. slow inflammability, to operate with a mixture of gas and combustion air supplied to the pilot-burner mouth thnough a mixer tube.

With the known pilot flame burners of this type, it is sometimes very difficult to obtain a quietly burning pilot flame, especially if the pilot burners are operated with gases of slow inflammability, for example earth gas or gas vaporized from liquids, both having an inflammability far below that of conventional city or utility gas. Such pilot flames, consuming only little gas are so instable that they may be blown out already by a slight draft or wind. Such pilot burners, therefore, constitute an appreciable source of danger.

It is an object of my invention to devise a pilot flame burner which eliminates the above-mentioned deficiencies and is capable of furnishing a quietly burning, stable flame that is not blown out by exposure to considerable draft or wind.

To this end and in accordance with my invention, a protective hood is seated upon the burner mouth of the mixer tube so as to form in front of the burner mouth an enclosure which envelops the pilot flame and is equipped with waste-gas outlet openings substantially at the height of the flame core. As a result, the pilot flame will burn within a space which is protected from external movements of air, but from which the waste gases can escape through the outlet openings of the hood. These waste gases still possess such a high temperature as to be capable of igniting the gases issuing from the nozzle of the main burner.

The protective hood to be seated upon the burner mouth is preferably given a cylindrical shape, and the waste-gas outlet openings are provided at the end of the hood opposite the burner mouth, namely in the cylindrical Wall as well as in the otherwise closed front end of the hood. If desired, however, the hood may be given a spherical, oval or ellipsoid shape.

The invention will be further described with reference to the accompanying drawing, showing, by way of example, a pilot flame burner according to the invention in longitudinal section.

The pilot flame burner 1 is conventionally provided with an elongated mixer tube 2 which receives gas of relatively low ignition speed, such as earth-gas or gas vaporized from lisuid, through a nozzle 3. The combustion air enters through an annular gap 5 whose cross section is adjustable by means of a jacket nut 4. The gas and the combustion air then pass through a Venturi nozzle 6 into the mixer tube 2 where they are intimately mixed with each other before they reach the burner mouth 7 at the other end of the mixer tube, to be burned in the pilot flame.

Placed upon the burner mouth 7 is a protective hood 8 which may be fastened to the mixer tube 2 by means of a threaded flange 9 screwed onto the tube 2 as shown. In

the illustrated embodiment the hood 8 is cylindrical. Its end remote from, and opposite the burner mouth 7 is provided with several gas outlet openings 9 and 10 which are located in the cylinderical wall 8' as well as in the planar end wall 8" of the hood. The gas outlet openings 9, 10 are preferably of circular shape and their crosssectional area is so large that the flame of the gas-air mixture, when being ignited from the outside of the hood will break through the openings 9, 10 to continue burning at the burner mouth 7 within the chamber formed by the hood.

For igniting the burner, the gas supply through the nozzle 3 is started so that the gas-air mixture passes through the Venturi nozzle 6, the mixer tube 2, the burner mouth 7 and the outlet openings 9, 10 into the environment. When now the gas-air mixture is ignited at one of the openings 9 or 10, the flame whips inward through the opening into the burner chamber and continues burning quietly in stable operation at the burner mouth 7. The waste gases then escape through the bores 9, 10.

The waste gas outlet 10 in the end face 8" of the hood is of particular significance for reliably preventing the accumulation of waste gas and also because it facilitates operating the pilot burner in any desired position without afiecting the stability of its pilot flame. Regardless of any particular wind or draft direction, the waste gases may escape through any one or more of the openings 9, 10.

Experience in practice has shown that a pilot burner equipped with a hood according to the invention provides a quiet and reliable pilot flame in any position of the burner, that is, regardless of whether the pilot burner is placed upright or in a slanting position or even upside down. In each case, the waste gases have been found to be reliably eliminated through at least one of the outlet openings without producing back-pressure, thus securing a reliable burning of the pilot flame at the burner mouth which is enveloped by the protective hood at a suflicient distance from the mouth.

I claim:

A pilot flame burner, particularly for gases of slow flammability, comprising a mixer tube with respective gas and air inlet means at one end and a burner mouth at the other end, a substantially cylindrical hood having one axial and ooaxially seated on said burner mouth and extending axially away therefrom so as to form in front of said burner mouth a chamber for enveloping a pilot flame of predetermined maximum length to burn at said month, said hood being closed at the end remote from said burner mouth and having waste-gas outlet openings in the form of bore holes located in said closed end and in the cylinderical wall near said closed end beyond the range of the predetermined maximum length of a pilot flame burnable at said month, said chamber being entirely enclosed by said cylindrical wall for a distance at least equal to said predetermined maximum length from said burner mouth.

References Cited by the Examiner UNITED STATES PATENTS 1,074,312 9/1913 Collins 12685 1,122,944 12/ 1914 Kennedy. 1,617,677 2/ 1927 Doble. 1,625,630 4/1927 Scott. 2,465,242 3/1949 Line 239601 2,591,626 4/1952 Sloan.

JAMES W. WESTHAVER, Primary Examiner. 

